This invention relates to a photographic printer which detects automatically from the data on a predetermined area of pixel segments whether the size of a film is a full size or a half size, and controls the printing aperture in the proper direction according to the data, and adjusts the opening of a mask of a printer opening, and further relates to a method for detecting and positioning frames of a film in the above mentioned photographic printers which can automatically detect and position an imaged frame in accordance with the size data on the original film, such as a film negative.
A size 135 film negative is exposed in frames of two sizes, i.e. a full size and a half size, except for special cases. A full-size frame is a rectangle having a longer side in the longitudinal direction thereof while a half-sized frame is a rectangle having a shorter side in the longitudinal direction thereof. When negative images photographed in such frames of different sizes and shapes are printed on a roll of photographic paper of a predetermined width, unless the full sized frame and the half sized frame are aligned in the proper direction by some means, they cannot be printed effectively by the same photographic printer on a photographic paper of the same size.
In the prior art, discrimination of a film negative into a full size or a half size is conducted by connecting films into an elongated length, inspecting the connected films visually or by a separate device, cutting a notch or applying a mark on a portion of the film or on a joint to be used as a means of memory, or storing such marks in a separate memory means such as a paper tape or a magnetic tape. This involves quite a troublesome procedure. Moreover, it is necessary to accurately position an imaged frame of an original film onto an optical frame at a photographic printer in order to print images in the frame optimally on a photographic paper. In the prior art, an optical sensor or mechanical sensor detects perforations which are provided on an original film at the rate of 1:1 with respect to original imaged frames or notches cut on the periphery of the film negative to position the frame. This conventional method, however, needs a projector and a light receiver arranged close to an optical frame for each optical sensor, or a microswitch for each mechanical sensor. Since sensors must be installed at particular positions, the structure inevitably becomes complicated and requires a great deal of labor to adjust the sensitivity or position.
There has been proposed another method which positions a frame by feeding a predetermined length of an original film, but this is defective in that positional deviation accumulates so as to deteriorate precision. Another method has been proposed to provide an optical sensor, such as a photodiode close to the periphery of the optical frame in the form suitable for the frames of the original film to directly detect frames of images and thereby position the frame in accordance with the result of detection by each optical sensor or sequential order. This requires a complicated control algorithm, however.